CodeChef Chef and Reversing

Posted on Edited on In 
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#include <bits/stdc++.h>
using namespace std;
using PII = pair<int, int>;
const int N = 100001;
int n, m, x, y, dist[N];
vector<PII> g[N];
priority_queue<PII, vector<PII>, greater<PII>> q;
int main() {
    scanf("%d%d", &n, &m);
    while (m--) {
        scanf("%d%d", &x, &y);
        g[x].emplace_back(y, 0);
        g[y].emplace_back(x, 1);
    }
    memset(dist, 0x3f, sizeof(dist));
    q.emplace(0, 1);
    dist[1] = 0;
    while (q.size()) {
        auto p = q.top(); q.pop();
        int d = p.first, u = p.second;
        for (auto &x : g[u]) {
            int v = x.first, w = x.second;
            if (dist[v] > d + w) {
                dist[v] = d + w;
                q.emplace(dist[v], v);
            }
        }
    }
    printf("%d\n", dist[n] == 0x3f3f3f3f ? -1 : dist[n]);
    return 0;
}
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#include <bits/stdc++.h>
using namespace std;
using PII = pair<int, int>;
const int N = 100001;
int n, m, x, y, dist[N];
vector<PII> g[N];
queue<int> q;
bool vis[N];
int main() {
    scanf("%d%d", &n, &m);
    while (m--) {
        scanf("%d%d", &x, &y);
        g[x].emplace_back(y, 0);
        g[y].emplace_back(x, 1);
    }
    memset(dist, 0x3f, sizeof(dist));
    dist[1] = 0;
    q.emplace(1);
    while (q.size()) {
        int u = q.front(); q.pop();
        vis[u] = false;
        for (auto &x : g[u]) {
            int v = x.first, w = x.second;
            if (dist[v] > dist[u] + w) {
                dist[v] = dist[u] + w;
                if (!vis[v])
                    q.emplace(v), vis[v] = true;
            }
        }
    }
    printf("%d\n", dist[n] == 0x3f3f3f3f ? -1 : dist[n]);
    return 0;
}
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#include <bits/stdc++.h>
using namespace std;
const int N = 100001;
int n, m, x, y, dist[N];
vector<pair<int, int>> g[N];
deque<int> q;
int main() {
    scanf("%d%d", &n, &m);
    while (m--) {
        scanf("%d%d", &x, &y);
        g[x].emplace_back(y, 0);
        g[y].emplace_back(x, 1);
    }
    memset(dist, 0x3f, sizeof(dist));
    q.emplace_back(1);
    dist[1] = 0;
    while (q.size()) {
        auto u = q.front(); q.pop_front();
        for (auto &x : g[u]) {
            int v = x.first, w = x.second;
            if (dist[v] > dist[u] + w) {
                dist[v] = dist[u] + w;
                if (w) q.emplace_back(v);
                else q.emplace_front(v);
            }
        }
    }
    printf("%d\n", dist[n] == 0x3f3f3f3f ? -1 : dist[n]);
    return 0;
}